this works great!! take the largest glass mason jar you can find. fill with hot boiling water, wrap in a shirt or towel. put it under the covers wiht you. it will slowly radiate heat under the covers all night! it creates a heat zone under there. i have NEVER been cold when i did this and i get chills really easy, especially when i fast. i actually learned this when i was quasi-homeless and sleeping outside in a sleeping bag, it worked. it was cold as heck but i was warm and snug. also hot tea with cayenne works, but not for very long.